Hi, I want to implement a StructuredBuffer in my shader so I can pass in an undefined number of lights. From my research I have decided that the best way to do this is to use a StructuredBuffer. However, I cannot find any good tutorials that document how to use it. Can anyone point me in the right direction? Currently, I am having trouble initializing the buffer in my C++ shader code; I am unsure about some of the parameters such as the StructureByteStride. Here is my current code which gives an error when calling CreateBuffer:

D3D11_BUFFER_DESC sbDesc;
		sbDesc.ByteWidth = sizeof(CLight);
		sbDesc.Usage = D3D11_USAGE_DYNAMIC;
		sbDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
		sbDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
		sbDesc.MiscFlags = D3D11_RESOURCE_MISC_BUFFER_STRUCTURED;
		sbDesc.StructureByteStride = sizeof(polygonLayout) / sizeof(polygonLayout[0]);

		D3D11_SUBRESOURCE_DATA subResourceData2;
		subResourceData2.pSysMem = (void*)_lights.data();
		subResourceData2.SysMemPitch = 0;
		subResourceData2.SysMemSlicePitch = 0;

		result = device->CreateBuffer(&sbDesc, &subResourceData2, &m_lightBuffer2);
		if(FAILED(result)){
			cout << "error" << endl;
			return false;
		}

		D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc;
		srvDesc.Format = DXGI_FORMAT_UNKNOWN;
		srvDesc.ViewDimension = D3D11_SRV_DIMENSION_BUFFER;
		srvDesc.Buffer.FirstElement = 0;
		srvDesc.Buffer.NumElements = _lights.size();

		result = device->CreateShaderResourceView(m_lightBuffer2.Get(), &srvDesc, &m_pSRV);
		if (FAILED(result)) {
			cout << "error" << endl;
			return false;
		}

And later to set the resource:

 D3D11_MAPPED_SUBRESOURCE mappedResource2;
 result = deviceContext->Map(m_lightBuffer2.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource2);
 if (FAILED(result))
 {
  cout << "error" << endl;
  return false;
 }

 size_t sizeInBytes = _lights.size();
 memcpy_s(mappedResource2.pData, sizeInBytes, _lights.data(), sizeInBytes);

 deviceContext->Unmap(m_lightBuffer2.Get(), 0);

 deviceContext->PSSetShaderResources(7, 1, &m_pSRV);

I am using ComPtr's for the buffer and the shader resource view:

Microsoft::WRL::ComPtr<ID3D11Buffer> m_lightBuffer2;
Microsoft::WRL::ComPtr<ID3D11ShaderResourceView> m_pSRV;

@MJP Thanks for your advice. I have managed to enable the debug layer so I'll look through it to see what's wrong.

So the error given by D3D is

D3D11 ERROR: ID3D11Device::CreateBuffer: pInitialData->pSysMem cannot be NULL. [ STATE_CREATION ERROR #65: CREATEBUFFER_INVALIDINITIALDATA]

Which I assume is a result of the following code:

D3D11_SUBRESOURCE_DATA subResourceData2;
subResourceData2.pSysMem = (void*)_lights.data();
subResourceData2.SysMemPitch = 0;
subResourceData2.SysMemSlicePitch = 0;

Since the light vector can be empty at the start, because it may not contain any lights, how can I initialize the pSysMem value when creating the subresource?

@mjp Setting pInitialData to NULL seems to have worked, but I found that an alternative solution was to set pSysMem to &_lights. Honestly I am not sure what the difference is. For now I'm just going with your solution.

 D3D11_BUFFER_DESC sbDesc;
 sbDesc.ByteWidth = sizeof(CLight) * 8;
 cout << sizeof(CLight) << endl;
 sbDesc.Usage = D3D11_USAGE_DYNAMIC;
 sbDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
 sbDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
 sbDesc.MiscFlags = D3D11_RESOURCE_MISC_BUFFER_STRUCTURED;
 sbDesc.StructureByteStride = sizeof(CLight);
 cout << sizeof(CLight) << endl;

 D3D11_SUBRESOURCE_DATA subResourceData2;
 subResourceData2.pSysMem = 0;
 subResourceData2.SysMemPitch = 0;
 subResourceData2.SysMemSlicePitch = 0;

 result = device->CreateBuffer(&sbDesc, NULL, &m_lightBuffer2);
 if(FAILED(result)){
  cout << "ERROR 1" << endl;
  return false;
 }

 D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc;
 srvDesc.Format = DXGI_FORMAT_UNKNOWN;
 srvDesc.ViewDimension = D3D11_SRV_DIMENSION_BUFFER;
 srvDesc.Buffer.FirstElement = 0;
 srvDesc.Buffer.NumElements = 8;

 result = device->CreateShaderResourceView(m_lightBuffer2, &srvDesc, &m_pSRV);
 if (FAILED(result)) {
  cout << "ERROR 2" << endl;
  return false;
 }

However when trying to set the output color of the object to one of the light colours at index 0 just to test if there is data in the buffer, this does not seem to work. The object is black when it should be white (1.0f, 1.0f, 1.0f).

struct Light {
   float4   PositionWS;
   float4   Color;
   float    Range;
   float    Intensity;
   float2  Padding;
};

StructuredBuffer<Light> lights : register(t9);

color = lights[0].Color.xyz;

Not the whole code obviously but you get the point… I will try to fix this and report the solution. Here is my code for how I load the lights vector into the shader resource slot:

D3D11_MAPPED_SUBRESOURCE mappedResource2;
 result = deviceContext->Map(m_lightBuffer2, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource2);
 if (FAILED(result))
 {
  cout << "ERROR: 3" << endl;
  return false;
 }

 size_t sizeInBytes = lights.size() * sizeof(CLight);
 cout << lights.size() *  sizeof(CLight)  << endl;
 memcpy_s(mappedResource2.pData, sizeInBytes, lights.data(), sizeInBytes);

 deviceContext->Unmap(m_lightBuffer2, 0);

 deviceContext->PSSetShaderResources(9, 1, &m_pSRV);

@mjp I downloaded RenderDoc as per your suggestion and it turns out the buffer was full of random data… I guess this is because CLight was a class and not a struct. I changed it to a struct and now everything works fine. Thanks for your help!!